Method for heat stabilization of synthetic thermoplastic yarns or threads

ABSTRACT

THIS APPLICATION DISCLOSES A TWO-FOR-ONE TWISTER WITH A TENSION-CONTROL TO THE COLLECTING BOBBIN WHERE A DENSE BODY OF THREAD IS WOUND FOR SUBSEQUENT HEAT-TREATMENT TO STABILIZE ELONGATION CHARACTERISTICS.

1971 P. R. PETERSEN 3,615,635

METHOD FOR HEAT STABILIZATION 0F SYNTHETIC THERMOPLASTIC YARNS ORTHREADS Filed Sept. 16, 1968 INVENTOI? PHILIP R. PETERSEN Umted StatesPatent US. Cl. 57--157 R 3 Claims ABSTRACT OF THE DISCLOSURE Thisapplication discloses a two-for-one twister with a tension-control tothe collecting bobbin where a dense body of thread is wound forsubsequent heat-treatment to stabilize elongation characteristics.

This invention relates to the heat stabilization of syntheticthermoplastic yarns or threads and, in particular, to the heatstabilization of polyester sewing threads. In particular, this inventionis an improved method of preparing a body of synthetic, thermoplasticyarn or thread for heat stabilization.

In recent years there has been a large increase in the manufacture andsale of permanent-press fabrics. These fabrics are usually subjected toa chemical treatment after weaving but before cutting and are ovenheat-treated after the sewing has been finished in order to makepermanent the shape and press desired. Cotton, which has beentraditionally used as a sewing thread, is unsuitable for use as a sewingthread to sew together permanent-press garments because it is notresistant to the chemicals involved and lacks the needed abrasionresistance in a permanently-pressed garment. Accordingly, the garment industry has resorted to the use of synthetic thermoplastic fibers forsewing threads. For example, sewing thread is made of these materials bytwisting staple length polyester fibers and thereafter doubling in theusual fashion. While these fibers produce a thread that is entirelysatisfactory from a chemical point of view and is quite compatible withthe oven treatment of pre-pressed garments, a problem arises inconnection with synthetic sewing thread that does not exist when cottonis used. This problem stems from the fact that the garment industry hastremendous inventories of sewing machines which have been designed tohandle cotton sewing threads and, because the stretch characteristics ofpolyester threads are quite different from those of cotton, seriousmechaical difliculties have arisen. To solve the elongation problemsuppliers of sewing thread have resorted to a heat treatment which hasbeen found to modify the stretch characteristics of polyester sewingthreads in order that those threads may behave sufficiently like cottonthat conventional sewing machines may be used without modification.

In the past, the heat stabilization treatment of polyester sewingthreads has been effected by winding a cylindrical yarn body on a hollowflanged metal support some seven to ten inches in diameter and ten ormore inches long. The thread is wound in such a way that adjacent coilstouch or nearly touch one another and thus form a very dense package upto an inch thick. This package is subjected to a heat treatment which ineflect makes the elongation characteristics, after the treatment, morenearly like those of cotton.

While sewing thread prepared in the foregoing fashion is entirelysatisfactory, it is somewhat costly to produce because, after doubling,there is a twisting operation, and after the twisting operation, thethread must be unwound from the package on which it is collected fortwisting and wound on the cylindrical body which supports it during heattreatment. Furthermore, the preparation of the thread "ice body for heattreatment requires that the winding be effected under conditions ofrigidly controlled tension. After heat treatment of the body, anotherwinding operation is required before the sewing thread is in a packagesuitable for shipment to customers. Any winding operation subjects thethread to some wear and thus causes some reduction in quality.

It is an object of the present invention to provide a method ofpreparing polyester sewing thread for heat treatment by which one of thewinding steps is wholly eliminated and the resulting economy is achievedwith an increase in the quality of the finished product.

It is a further object of the present invention to twist and collectsewing thread under controlled tension, as part of a single operaiton,whereby there is avoided the intermediate winding step between twistingand the winding of the package shipped to the customer with resultingreduction in cost and increase in quality.

Other objects and advantages of the present invention will be apparentupon consideration of the following detailed description of a preferredembodiment thereof in connection with the annexed drawings wherein thesingle figure is a schematic view in end elevation and in section of atwo-for-one twisting machine modified for the practice of the method ofthe present invention.

In the drawing, the numeral 10 designates a stationary yarn body whichis located around a hollow twister tube 11 provided with a flier 12which functions to prevent the rubbing of the thread on the outside ofthe package. Thread is drawn upwardly from the body 10 through the flier12 and passed downwardly through the tube 11. Yarn body 10 is located ina container 12a. From the lower end of the tube 11 the thread passesthrough a rotating disc 13 from which it is thrown out radially to bedrawn upwardly between the container 12a and balloon control shield 14to a pigtail guide 15. From pigtail guide 15 the yarn is led over agodet 16 comprised of a driven roller 17 having a frictional threadcontacting surface and an idler 18 having grooves in the surface tocause the yarn to pass in a generally helical pattern back and forthbetween rollers 17 and 18 enough times so that the speed of drivecylinder 17 becomes an anchor point for the controlled stretching whichtakes place between godet 16 and an aluminum drum 19 which constitutesthe bobbin upon which the thread is collected.

Bobbin 19 is a hollow aluminum cylinder having flanges at each end, thenear flange 20 being apparent in the drawings. The thread is laid up bya so-called parallel traverse mechanism between the end flanges of thecylinder 19 as a tightly wound body up to one inch thick, having aninternal diameter of about seven to ten inches and a length of about teninches. Preferably the traverse is adjusted to lay the yarn up with aminimum helix angle or pitch such that adjacent threads on each coursetouch one another. This is not absolutely necessary, however, since anywind that produces a very dense body of thread is satisfactory. When therequired amount of yarn has been wound, the cylinder 19 is dotted andsubjected to heat treatment in the usual fashion.

The tension to which the thread is subjected between the godet 16 andthe surface of the cylinder 19 is very critical. For example: A 50/2cotton count (213 den. total) thread is spun of Kodel high tenacitypolyester fiber (Eastman Chemical Products, Inc.) and twisted on thetwo-for-one twister utilizing twenty turns per inch twist and settingthe tension at thirty grams while winding onto an aluminum bobbin suchas the part 19 shown in the drawings. This bobbin can contain a layer ofthread approximately /8 inch thick and is later heated in an oven untilall of the thread on the bobbin reaches 375 F. The resulting thread isthen ready for use after Winding and lubricant application.

- While the illustrated form of the invention shows tension developedbetween a godet and a rotating drum, it may be possible to impartsuflicient tension by substituting a drag device for the godet 16.

While the invention has been described in connection with a two-for-onetwister, it is equally applicable to any type of up-twister where thecollection of the yarn is independent of the magnitude of the twistimparted to it. The illustrated two-for-one twister is a conventionalone, as manufactured by Socit des Mcaniques Verdol.

While the invention has been described in conjunction with thepreparation of sewing thread, it is applicable to other uses where thecollection after twisting is required to be under conditions of tensionindependent of the twisting operation itself.

What is claimed is:

1. The method of preparing thermoplastic threads for heat treatment toimprove the initial elongation characteristics that compriseswithdrawing yarn from a package along a path While rotating the yarnabout the axis of said path to a point of tension control, drawing yarnfrom said tension control point to a winding region under uniformconditions of tension and there winding a hollow thread body ofsuperimposed courses of thread, each course being laid up at a helixangle so small that the adjacent coils of thread touch one another, saidbody defining a hollow core having an internal diameter no less than tentimes the radial thickness of the thread body and thereafter heatingsaid thread body.

2. The method of preparing thermoplastic threads for heat treatment toimprove the initial elongation characteristics that compriseswithdrawing yarn from a stationary package to a point of tension controlalong a predetermined path while rotating the yarn about the axis ofsaid path to impart twist thereto, drawing yarn from said ten- 41 sioncontrol point to a winding region under uniform conditions of tensionand there winding successive, superimposed courses of thread to producea hollow thread body having a core with an internal diameter no lessthan ten times the radial thickness of the thread body, the adjacentcoils of each course of thread being close enough to one another to makea very dense thread body and thereafter heating said thread body untilall parts of it have reache a temperature of 375 F.

3. The method of preparing thermoplastic threads for heat treatment toimprove the initial elongation characteristics that compriseswithdrawing yarn from a stationary package and drawing it to a point oftension control through a path passing axially through and then besidesaid package while rotating the yarn about the axis of the package toimpart a two-for-one twist, drawing yarn from said tension control pointto a winding region under uniform conditions of tension and thereWinding a hollow cylindrical body having a core with an internaldiameter no less than ten times the radial thickness of the thread body,adjacent coils of each course of thread touching one another andthereafter heating said thread body.

References Cited UNITED STATES PATENTS 2,158,607 5/1939 Bochmann2423-128 2,729,051 1/1956 Clarkson 57-'62 X 3,277,640 10 1966 Colombu etal. 57-6 2 3,423,922 1/1969 Smith 5762 X 2,421,336 5/1947 Kline et al.2872 JOHN PETRAKES, Primary Examiner US. Cl. X.R. 5734 HS, 62

